Method of and apparatus for drying



Dec. 8 1925- G. D. HARRIS METHOD OF AND APPARATUS FOR DRYING 2 Sheets-Sheet 1 Filed May 6, 1921 v H V 5 0 0 o i. a I] 0 0 DeC. 8, 1925- I G. D. HARRIS METHOD OF AND APPARATUS FOR DRYING Filed May 6, 1921 2 Sheets-Sheet 2 Patented Dec. 8, .1925.

UNITED STATES PATENT OFFICE.

GORDON DON HARRIS, OF ISLIP, NEW YORK, ASSIGNOR, BY MESNE ASSIGNMENTS, TO I THE INDUSTRIAL DRYER CORPORATION, OF STAMFORD, CONNECTICUT, A COR- PORATION OF CONNECTICUT.

METHOD OF AND APPARATUS FOR DRYING.

Application filed May 6,

To all whom it may concern:

Be it known that I, GORDON DON HARRIS,

a citizen of the United States, residing at Islip, county of Suffolk, and State of New York, have invented a certain new and useful Method of and Apparatus for Drying, of which the following is a specification.

This invention pertains to the art of drying wherein the operation is conducted in a partial vacuum and within'a tightly closed chamber to which no outside atmospheric air is admitted during the operation of exchanging heat for moisture, and within which chamber the circulation of the drying atmosphere is effected by successively expanding and condensing said atmosphere through the agency-of appropriate heating means and of condensing means. The

rapidity of flow of the drying atmosphere Within the closed chamber is controllable by the action of the condenser in chilling the atmosphere and by the action of the heater in expanding said atmosphere, provision being made for controlling at will the flow ofa cooling agent within the condenser and for regulating the heating means so as to give off more orless heat units to said, atmos here.

T e drying atmosphere is conditioned with reference to humidity by the absorption of the aqueous vapors from the material under treatment, and the action of the condenser in the elimination from said atmosphere, of more or less aqueous vapors;

and, furthermore, said drying atmosphere is conditioned in respect to temperature b v the operation of the heater. It is thus madZ possible to regulate the moisture and heat content of'the drying atmos here, and such 40 conditionin of the atmosphere when per- ,formed wit in a chamber in which is established and maintained an atmosphere at a pressure less than that of the outside atcmosph'eric air enables the treatment of the material to be conducted in a. manner to preclude oxidation of the material and to prevent the formation of a film on the surface thereof, besideskeeping the pores of 1921. Serial No. 467,492.

such material open for the free exit of the aqueous content of said material.

According to this invention, the moisture content of the drying atmosphere is determined by the action of the condensers having means for controlling the flow therethrough of a cooling medium whereby the condenser is regulatable for its surfaces to be kept in a cold condition, or at the dew point, for condensing the aqueous vapors present in such atmosphere, the condensate being discharged from the circulatory path. Concurrently with the condensation of the aqueous and volatile vapors, the drying, atmosphere is chilled so that it descends within one part of the circulatory path, following which descent the atmosphere is expanded by the action of heating means situated in another part of the circulatory path,

whereby the successive condensing and expansion of the atmosphere attains or results in the required circulation within the chamber to which atmospheric air is not admitted during the treating period. The aqueous vapors from the material are absorbed,.at least partially, by the flowing atmos here, the same being-imtially expanded by t e action of the heaters, which expansion of the atmosphere within the closed chamber tends at certain periods, more or less frequent, to establish within the chamber a pressure in excess of the outside atmos heric'pressure due to the expansion of t e atmosphere, whereupon the pressure within the chamber o erates a valved exit, to open the latter and t us permit the escape from the chamber of some of the expanded air until'the pressure within the chamber, is less than the pressure of the outside atmospheric alr, the

efiect of which is to allow ,the valve at the exit to be closed by atmospheric pgessure, whereby the valved exit fromthe ch mber is opened automatically for the exit of" a ;ce r-.

rtion of the atmosphere within. the cham er, and which exit'remams insaid' 1 tain' pro openedcondition until the internal. pressure is reduced to a sure (14.7),an

thereupon the valved exit is point belowatmospheric pres-' her, and

closed automatically by the atmospheric pressure exceeding the internal chamber -pressure.

Other functions and advantages of the. 1nvention=will appear fromv the following description taken in connectionwith the drawings, wherein-5 Figure 1 is a vertical sectional elevation through a drying apparatus wherein the material is suspended-w thin the treating cham'-' Figure 2 is a vertical longitudinal section of another embodiment of. the invention equipped with-trays or other. means forsup T The, interior ofthe housing is divided by walls 6, preferably insulated, said; walls being arranged to produce a circulatory path for the drying atmosphere with a main chamber B- for the ascent of the drying atmosphere and with one or more other chambersC C for the descent of sucha-tmosphcre. The main chamber B is relatively large in cross'section as compared with the other chamber or chambers; for convenience the chamber B- may be referred tolas the ma- I terial or treating chamber, whereas the other chambers G G will be designated as the. cooling chambers. The material ,to be treated is supported within chamber B'by any known means, but as shown in Figure 1 the eration.

chamber is adapted for the hanger rods D by'whichthe materiahsnch as rubber slabs,

sheet cork, etc.,' is suspended in -a manner toprovide spaces for the circulation ofthe drying-atmosphere around and in contact with said material.

The workman obtains access to chamber B'through suitable doors,

'as usual, which doors must or should be closed tightly in conducting the drying opw Across the lower part of chamber B is a floor E and a'crossthe top of said chamber is a' roof The 'floor and the roof are lshown as extending'parallel to the bottom and the top, respectively, of the housing, 'whe'rebyh'heater chamber E is rov'id'ed below chamber B [and a horizonta fl'ue or duct F is formed 'over said chamber, said heater chamber E being incommunication at its ends with the side cooling chambers Q0 "and horlzontalflue F-' being in com- 1 munication also, with the cooling chambers O .C, said c 'amber Eandflue -F coustituh,

ing parts 'ofthe closed circulator .path for the drying atmosphere. The

oor E of chamber B is provided with orts e by which 7 the atmosphere, heatedfwit in thechamber E", is free'to 'ascend'into chamber B, and in like manner, the roof F. is provided with memes portsf through which the atmosphere; flows.

from chamber B into the fiue'F', and thence to the "cooling chambers G C.. p

A heating means of any appropriate character ispositioned within chamber E;

as shown said heater is embodied: in the form of coils G, and-provision is made, as

usual, for controlling the flow of a heating medium-to said coils. s

The cooling or condensing means is'shown' as vcoinprisnug corls H H positioned within chambers G ,C, said coilsbeing provided with means for controllin g the flow of a cooling medium ,to and through said coils; said cooling medium bein either the usual refrigerating agent, or. "co (1 water, 'or anyother agent acting to chill'the surfaces-or coils H H to at least the temperature known as the dew point, necessary. to: condense the aqueous content of: the drying atmosphere upon the surfaces of said coils. The moisture of condensation, or the condensate, collecting upon the surfaces of the cooling coils is discharged; f rom the circulatory path.

ofth'e drying atmosphere; as shown, the condensate is free to drip from the cooling coils into collecting troughs .cp'ositioned at the bottom of the chambers C, and said troughs are, or may 'obviouslybe' arranged to discharge the condensate to the exterior ofthe housing. a

I .s a vent provided with a valve 5, the

latter being closed normally by the external atmospheric pressure. .S aidjve-nt is shown as-a pipe extending through the top of the housing for free communication -with the ice interior thereof. The valve associated with saidvent is or may be of any suitable con-a 0 -form; but said valve is positioned OIT xposure to the pressure of the dryin-gfl atmosphere within the housing and to the pressure of the atmospheric airfexterior'to said housin saidvalve beingiheld to, its

seat normal y by atmospheric pressure for thepurpose ofcncluding the inflow of out side atmospheric air to the housin as well as to cut ofl normally the outflow o the dry ing atmosphere from said housing.

' In operation, thematerialis'hun within the chamber B and the .apparatus'ls closed tightly for excludingthe mgresscf outside atmospheric air during the drying period.

. Steam issupplied to heater'G auda cooling I heater upon the atmosphere present in cha n 6" berE' tendingv to eirpand .the atmospherafil medium to condensers. the action of the whereas the cold surfaces of the 'coilsH'i, chills the atmosphere, a's-a result ofzwhich The jflolw of, the atmosphere heated within the atmosphere must atesjwithi'n tlie closed" circulatory path constituted by chamber -B,'top.,flue F! side f i chambers, C G,- jand' bottom chamber EC expansion and-chillin'gthe atmosphere ci'ron iao phere flowing upwardly within chamber B is free to have the desiredcontact with the material whereby the heat units carried by the atmosphere are given off to the material to effect the exchange of heat for moisture,

the aqueous contentof the material being' given off and taken up bythe atmosphere which thus constitutes the carrier for heat and moisture. The atmosphere flows out of chamber B throu 11 ports f and is directed by flue F towar and into the side chambers G C, whereupon the contact of the atmosphere with the'cold surfaces of the condensers H has the effect of condensing the aqueous content present insuch atmosphere and of chilling or reducing the temperature of such atmosphere, with the result that the atmosphere descends within the chambers C C and thence flows into chamber E, to be again expanded by the action of heater G.

The atmosphere is thus expanded andcondensed, the effect of which is to insure circulation within a closed path due to the dif-v ference in temperature brought about by-the action of the condensers and heater, and during the cycle of operations the atmosphere carries heat to the material so as to drive off the moisture, takes up the aqueous content of such material, carries vthe mois ture to the condensers, and gives ofl a percentage, or substantially the whole,of such moisture by contact with the chilled surfaces of the condensers,.-all of which cycle of operations are performed withoutthe aid of any moving parts and within a chamber closed againsttheingress of outside atmospheric air. The alternate expansion and condens' tion of the atmosphere required to effectuat the circulation, and the vaporization and expansion of the aqpeous content of the atmosphere by the heating operations, has the effect of increasing the pressure of the atmosphere to a point where such, pressure within the chamber exceeds the pressure of the outside atmospheric air, the result of which is to open vent valve i'for' such a period as' will permit the exit of a certain volume of the drying atmosphere without,

however, admitting atmospheric air to the 3 chamber for the reason that upon the reduc- V tion of the pressure within the chamber the vent valve 2' is closed automatically by the pressure of the external atmosphere. The

vent valve is opened initially or intermittently for the exit of a certain proportion of 'within the chamber B an atmosphere the the drying atmosphere, thus attaining raritication of the atmosphere, more or less, within the closed circulatory path, with the result that there is established and maintained normal pressure of which is less than the pressure of the outside atmospheric air.

' At the beginning of the operation, the

temperature of the atmosphere within the apparatus is increased above the tempera- .ture that prevails in the normal operation,

and such increased temperature results in expansion of the contained atmosphere, with the result that the pressure within the apparatus is initially increased and the vent valve is opened for'the escape of some of the con tained air, resulting in a decrease in the pressure of the contained atmosphere below the pressure of the outside atmospheric air.

thus dried in a partial vacuum and by the circulation'of an atmosphere the tempera turea'nd humidity of which is, controllable with a view to treating the material under conditions which drives off the aqueous content thereof while leaving the pores open for the free exit of such aqueous content to the surface of the material, whence it is picked up and carried oil by the atmosphere, to be condensed by contact with the eold surfaces of the condensers. I

The constructional form of apparatus de features hereinbefore described, although the arrangement is somewhat different with picted in Figure 2 embodies the essential The exterior housing A is provided at its f top with the valve controlled pressure exit I. and within said housing is arranged the walls 6 .to'produce the material chamber B and side chambers C. Near the bottom are artitions E corresponding in part to floor and at the top is a roof F witha central port f. Below the material chamber B is a, heater chamber E containing a heater G with appropriate means for regulating the inflow thereto of a heating medium such as steam. The roof F is parallel to the top of housing A for the formation-of a flue F 3 leadin in two directions 'to the side chambers densers H in the form of coils with appropriate meansfor controlling the flow therein of a cooling agent, suitable collection troughs c'being provided below the condensers for the reception of the condensate dripping from said condensers.

Within the material chamber B are trays J arranged in vertical series, the trays of each series being relatively spaced to pro- Ian ', and within said chambers are conduce flow channels between said trays. The vertically "grouped trays are separated to? produce a central space j and side spaces j,

chamber," being supported therein b appropriate slides in the form of ang e irons.-'

As shown, the lower horizontal trays. cooperate with the parts E to form the bottom of the treating chamber B. The baflies J J are'positioned in the horizontal planes of other trays and. in such relation" thereto and to each other as to form a plurality of tortuous circulatory atmosphere. 4 v I p K arereheaters or boosters 1n the form of coils positioned within the circulatory paths for the drying paths constituted in part by the flow' channels intermediate the trays, said coils being in thevertical planes of said trays, and each coil being in the channelbounded by the .trays above and below said channel. -The' reheaters or boosters are supplied with a heating medium of a deslred character, suchas steam, and in the course of the drying operationsaid coils give off heat to the drying atmosphere and to the contents of t trays for the purpose of reheating the air to compensate for the drop in temperature moisture is expedited with an attendant occasioned by the exchange of heat for moisture, whereby the primary heater- G acts mainly to heat the atmosphere to a desired temperature, whereas the reheaters perform the function of boosting the atmos- 'phere with a view either to keeping the temperature constant .or to increase the temperature in order to initially-expand the.

indicating the moisture content of the at atmos here so' as to" increase the ressure font 6 operation of the exit va ve, the successive operationsof.-which permits a certain proportion ofthe drying atmosphere to escape whereby-the drying atmosphere is increasingly rarified and the drying 'oper-' ations' are conducted in a partial vacuum to the end that the exchange of heatJfor economy of time and energy:

1 The operatlon of the apparatus shownin Iiigure 2 is similar to that described int connection with Figure 1, the atmospherebeingexpanded and condensed 'for eifectijng' circulation within a closed "path "to .'-whichatmospheric air is excluded during the dry-' mg period. The trays having-been filled and placed 'Wi'thin'the chamberand the doorsti' htly closed, steam is supplied to the heater 5 and the reheaters K, and a cooling agent sf w tted to the condensers. The atmosphere isse'xpanded by heat. units given oif by the heater and .reheaters,- and is chilled. or cooled-by contact with the cold surfaces of the condensers, thus setting the" as is or maybe necessary to expand the atinated.

tended, without requiring constant manual atmosphere into motion by the successive expanding and chilling thereof, due to the change in temperatures. The atmosphere is directed to flow in a definite path :estabthe middle part of chamber E and flowing in two directions within the spaces or channels intermediate the trays and emerging from the chamber B by way of port f into top flue F, and thence to the cooling chambers. The circulation established-by the diff ference in temperature within diiferent zones of the. lrousing continues without interruption or manual operation for such a period mosphere and attain a pressure exceeding the external atmosphere pressure, whereupon the vent valve is opened and a certain proportion ofthe expanded atmosphere escapes, resulting in a reduction of the internal pressure, the repetition of which operations ultimatey attains a rarification of the atmosphere constituting the medium by which the moisture content of the material is elim- It is desired to call attention to theffact that in my invention no moving parts are employed, such as blowers, and no atmosheric air is admitted to the ap arat-us durmg the drying period. As usua the apparatus is equipped with "appropriate thermometers for indicatingthe temperature at different points, and it is equipped-also with wet and dry bulb thermometers (hygrodeiks) positioned'at appropriate points for time it is possible to continue the drying operation for a period, more or less ex attendance.

my invention Inwhichflis below the pressure of the outside atmospheric air, and it includes, also, the circulation of such drying atmosphere in an attenuated or'rarified condition, which circulationis efl'ected within aclosed' path by alternately expanding (heating) and chilling such atmosphere The drying atmosphereis heated initially to expand it andincrease the pressure within the appatratus, whereupon the valved vent is openedhy-such excess of the internal pressure, resultin in the emape of some of'the andheater E whereas within the expanded atmosphere, theefiect of which is to attenuate the internal atmosphere and to reduce its pressure below that of the outside of the atmospheric air. At the periods I of expansion of the atmosphere the flow of a cooling medium to the condensers is or may desirably be arrested until the desired re-,

' duction in pressure of the internal atmoshere is attained. The apparatus may thus he vented by opening the vent valve, which valve normally is closed by the ressure of the outside atmospheric air, an said vent valve being opened only at such periods as when the internal atmospheric pressure ex-.

, atmospheric air is excluded and within which circulatory path a. partial vacuum is established and maintained, and setting up a circulation of a drying atmosphere in an attenuated condition within said closed circulatory path by alternately expanding and condenslng such atmosphere.

2. In the art of drying, the process which consists in placing the material to be dried within a chamber provided with a gravityclosed vent and which chamber constitutes a part of a closed circulatory path from which outside atmospheric air is excluded and within which circulatory path a partial vacuum is established and maintained heating a drying atmosphere at a definite point within said circulatory path to a pressure exceeding that of the outside atmospheric air, thereby opening said vent tothe exitof some of the drying atmosphere, and cooling the drying atmosphere within said circulatory path at a,point remote to the heating om I p 3. In the art of drying, the process which consists in establishing a partial vacuum within a closed circulatorypath from which outside atmospheric air is excluded, and al ing the same at ternately expanding and condensing a rarefied drying atmos here by heating and cooldifierent zones within said circulatory path.

4. In the art of drying, the process which consists in venting a closed circulatory path to establish a partial vacuum therein, and alternately expanding and condensing a rarefied drying atmosphere to set 'up a circula,-.

y Pa 7 5. In the art of drying, the process which consists in placing the material to be treated within'a closed circulatory path from which outside atmospheric air is excluded during the treating period and within which circution of said atmosphere within said circulalatory path is established an attenuated drying atmosphere the pressure of which is be-.

tion Within said circulatory path by the difference in temperature established at distinctly different zones, and reheating the.

drying atmosphere during the period of its 'fiow into contact. with the material.

6. In the art of drying, the process which consists in placing the material to be treated within a tortuous flowpassage constituting a part of a closed circulatory path from which outside atmospheric air is excluded during the attenuated drying period and within which circulatory-,pathis established an attenuated drying atmosphere the pressure of.

which is below that of the outside atmospheric air, setting up a flow within said circulatory path and the tortuous flow passage of a drying atmosphere by expanding and chilling the same at definite zones within said circulatory path, and reheating the drying atmosphere in the periods of. the flow into contact with the material and within the tortuous flow passage. y

7. In the art of drying, the process which consists in placing the material to be treated within a closed circulatory path from which outside atmospheric air is excluded during the drying period and within which circulatory path is' established an attenuated drying medium the pressure of which is below that of the outside atmospheric air, setting up a flow of a drying medium within the.

circulatory path by successively expanding and condensing said atmosphere within.

definite zones of said circulatory path remote one to the other and for such a period as, ultimatelyresults in an increase of the pressure of said drying atmosphere until such pressure exceeds atmospheric pressure, and venting the closedv circulatory path'by utilizing the pressure of the dryingmtmosphere therein in opening a valved exitnormally maintained in a closed condition by atmospheric pressure.

8. In the art, of drying,. the process which consists in venting a closed circulatory path 'from which outside atmospheric air. is excluded to establish a partial vacuum within said circulatory path, and setting up the circulation of a rarefied vdryin 7 atmosphere withinsaid circulatory path y subjecting consists inventing a closed circulatorypath from which outside atmospheric air is exsaid rarefied atmosphere .to theaction of cluded and establishing within said path a' drying atmosphere in an attenuated condition the pressure of which isbelow the atmosp'heric pressure of the outside air, and

' setting up the flow of saiddrying atmosconstituting 'a part of a closed circulatory phere within said circulatory path by successively expanding and cooling the same.

10.". In a drying apparatus, ahousl-ng provided with a material containing chamber path from which outside atmospheric air is excluded and within which is established a drying atmosphere-in an attenuated condi-l tion, the pressure of which attenuated drying atm'osphereis below the pressure of the outside atmospheric air, means'cfor expand= ing the attenuated drying atmosphere by heating-the same at a definitepomt m the circulatoryfpath, and means ,for condensing theattenuated drying atmosphere by. cooling the same at a definite point within the circulatory path, said condensing and cool ing means being remote to'the heating and expanding means.

11. In a drying apparatus, a housing pro I vided with a material 'containingjehamber constituting a part of a closed circulatory path from which outside atmospheric air is excluded and withiniwhich is establishedfa drying atmosphere in an attenuated condition, the pressure of which attenuated dry- 80 ing atmosphere is below the pressure of the outside atmospheric a1r,heating'means positioned within the circulatory path for ex- Y chilling aid attenuated drying "atmosphere,

saidimat ial containing chamber being intermediate said heating means and said coirdensing means.

.. path from whi vided with a material containing chamber constituting a part of a closed circulatory c outside'atmospheric air is excluded and within whichis established a drying atmosphere in an attenuatedcolidi:

tion, the pressureof which attenuated d1 ing' atmosphere is below'the pressure of .t e

outside atmospheric air, meansforexpand ing the attenuated atmosphere by.- heating same at a definite point in the circulatory path, -cbndensing means for chilling the attenuated drying atmosphere, said con- (lens ng and chilling means being situated within the circulatory path at a point re}; mote to the heating-means, and additional ent within a c ofsed circulatory path by' eat- :ing such-atmosphere until the pressure saitheric heating means positioned with the material containing chamber for boosting theattenuated dryin'g'atmo'sphere as it flowsinto con- I tact with moist material. I

13-. Ina drier, a housing provided with a closed circulatorypath from which outside .atmosphericair is excluded during the dry- ,12. In'-a drying apparatus,a housing :pro-

a condenser.

drying'atmosphere for setting the same in motion by the-difference in temperature, and a valved controlled vent in communication with the circulatory path, said vent being normally closed by the pressure of the external atmospheric air and said valve being opened by the d ing atmosphere when the pressure within t e-housing exceeds that of the external atmospheric air.

14. In a drier, a housing provided with a closed ci rculatory path including a material-chamber and fromwhich closed path ,outside atmospheric air is excludedduring the drying: period and within which circu latory pat is established an attenuated drying atmosphcrd'the pressure of which 1111-" der working conditions is below the pres "sure of the outside atmospheric air, ma-

terial supporting means positionedwithin said material. chamber for cstablishin therein a tortuous passage for the back an temperature established in different zones forth flow of the attenuated drying atmo'ss phere, heating means and condensing means within different parts ,ofsaid circulatory path for. setting up the flow of said attain-j within the circulatory path, and reheating" means within the tortuous'passa vtermedia'te .the material supporting means. -15. In a drier, a'housin provided'with a closed circulatory path 'inc uding. amaterial.

chamber andtrom which closed path outside atmospheric air is excluded' during the drying period, material supporting means posis tioned within 1 said material chamber for establishing therein a tortuouspassage for, v the back and forth flow of a drying atmos phere, heating means and condensing means within different parts of said circulatory n path for setting-up the how of a drying atmos here by. a difierence'jin temperature established in dijfierent zones within the c' irculatory path, reheating means within the qtortuous passageiand intermedifitr the ma--' a terial" supporting means, a; normally closed vent in communication with said closed-circulatory-path, said vent, being 0 ed the pressure of he drying atmosp ere, and. means for collecting the a moisture of. con 7 densation deposited upon the surfacesjof the y 16. "In'the art consists in exandmg'the atmosphere. res

and in low of the which pressure of the outside atmospheric air, thereby attaining an attenuated 0r rarefied drying atmosphere within said path, and al-- present within a close'd circulatory path for expanding such atmosphere and increasing the pressure thereof until it exceeds the pressure of the outside atmospheric air, opening an exit from said closed path for the escape of such expanded atmosphere, thereby reducing the pressure of the atmosphere until it acquires an attenuated or rarefiecl'condition within such closed path, alternately chilling and heating the attenuated atmosphere for effecting the circulation thereof within said closed path, and dividing the flow of the circulating atmosphere as such atmosphere emerges from the presence of the material under treatment.

In testimony whereof I have hereto signed my name this 29th day of April, 1921.

GORDON DON HARRIS, 

